'Amorphous solids' are a strikingly broad category of materials, ranging from colloidal pastes and concentrated emulsions to metallic glasses. Nonetheless, experiments and numerical simulations have evidenced a similar scenario at the basis of the deformation and flow of these very diverse materials, a scenario made of phases of elastic loading interspersed with episodes of plastic relaxation; this relaxation takes the form of swift and localised rearrangements between particles [1-2], which allow the local stress to be relaxed and redistributed to the rest of the material, which can give rise to a cascade of subsequent rearrangements.
Elastoplastic models [3] have emerged on the basis of this simple scenario and handle the material as a collection of mesoscopic blocks that alternate between an elastic regime and plastic relaxation; these models purport to be the analogue of the 'Ising model' for the mechanics of amorphous solids. Their emergence has opened a new avenue for the Statistical Physics-based study of questions that originally belonged in the realm of Mechanics [4].
In this boiling field, one important link is still missing, though: the connection between the actual response of particles (i.e., molecules, colloids, or droplets) and the rules governing the aforementioned mesoscopic blocks. The internship will be an endeavour to bridge this gap by (i) analysing the behaviour of a mesoscopic material region with the help of atomistic simulations and (ii) constructing a fictitious energy surface that can reproduce the main (statistical) features of the observed behaviour
The ideal candidate has a strong inclination for numerical simulations (Molecular dynamics) and a background in Statistical Physics or Solid State Mechanics; skills in machine-learning and AI techniques would be an asset. The intern will be based at iLM, in Villeurbanne (near Lyon).
References :
[1] SCHALL, Peter, WEITZ, David A., et SPAEPEN, Frans. Structural rearrangements that govern flow in colloidal glasses. Science, 2007, vol. 318, no 5858, p. 1895-1899.
[2] ALBARET, T., TANGUY, A., BOIOLI, F., et al. Mapping between atomistic simulations and Eshelby inclusions in the shear deformation of an amorphous silicon model. Physical Review E, 2016, vol. 93, no 5, p. 053002.
[3] NICOLAS, Alexandre, FERRERO, Ezequiel E., MARTENS, Kirsten, et al. Deformation and flow of amorphous solids: Insights from elastoplastic models. Reviews of Modern Physics, 2018, vol. 90, no 4, p. 045006.
[4] LIN, Jie, LERNER, Edan, ROSSO, Alberto, et al. Scaling description of the yielding transition in soft amorphous solids at zero temperature. Proceedings of the National Academy of Sciences, 2014, vol. 111, no 40, p. 14382-14387.
